NEED HELP FAST - obc issue

[Bimmerfanatik]

Hey guys - trying to finish the blue 87 es for tomorrow's pickup, but we've run into a problem. It was running perfectly fine, but I tried to remove the OBC harness to try in another car. Now I've put it back in, and it won't start.

We've gone through every plug that the OBC harness has, and made sure it's plugged in tightly and in the right spots. We tried my euro OBC, which worked (lit up, all functions were displayed) but now all I get is a lit blank screen. Pulled one out of the 86 es - same thing. The IS OBC doesn't even light up.

Still no gas. When I pull the fuel pump relay (middle relay) and try wiggling it while cranking, I get nothing. When I wiggle the main relay, it has power.

What am I missing here? Mark (wastedincome) and my friend Matt are there now, so any advice I can relay to them. Please let me know asap!

[Bimmerfanatik]

PS.

There are two green 4 prong plugs that plug into the OBC module under the driver's dash. One was plugged in when the car came in, the other was jumpered and taped off. Upon seeing this, I had Matt pull the jumpers and try to figure out why it was like this. Unfortunately, when he did, he didn't note what spots the jumper was in, and when we went to put it back in, we fried the ground wire. What I'm afraid of is that we've also fried something else. The question is - WHAT?

[UNHCLL]

does the OBC even light up while its plugged in and the car is on?

[Bimmerfanatik]

does the OBC even light up while its plugged in and the car is on?

It lights up, but nothing displays. It did earlier in the troubleshooting process...

[turnofftheradio]

if I remember...
the jumper is probably due to a bad solder in the obc box, easy fix, mine was bad too. 2 9mm nuts hold the obc relay in, the bottom kinda pops out to get to the board. or maybe the fuse inside it, there is a glass one in there or the obc itself, I can't remember.

not sure if that is helpful or not after reading it...

[UNHCLL]

then its getting memory power, and not switched power.

Similar to what happens when you fuck up the wiring on the stereo. OBC will light up, but not display anything.

Have them check the connections for switched/constant power.

[UNHCLL]

Oh, and let me know when I get to say "I told you so"


;) good luck scotty. keep us posted as you move forward

[Bimmerfanatik]

if I remember...
the jumper is probably due to a bad solder in the obc box, easy fix, mine was bad too. 2 9mm nuts hold the obc relay in, the bottom kinda pops out to get to the board. or maybe the fuse inside it, there is a glass one in there or the obc itself, I can't remember.

not sure if that is helpful or not after reading it...

Swapped the OBC box for a known good one - still no luck. Tried every combination of jumper choices, again, no luck. PS - they're 10mm nuts holding the ABS comp in the way, and 6-8mm plastic nuts holding in the OBC unit.

[Bimmerfanatik]

then its getting memory power, and not switched power.

Similar to what happens when you fuck up the wiring on the stereo. OBC will light up, but not display anything.

Have them check the connections for switched/constant power.

Elaborate on this - I'm fried as much as the OBC, so I can't think straight.

[UNHCLL]

The wiring for the OBC is tied directly into the wiring for the factory head unit. If you've messed up the wires on the HU, the OBC wont work. Does the radio still work?

I'd suggest checking the fuses in the fuse box that are related to the radio/OBC
then check the wires leading into the OBC to try and match them up for switched and constant power


I'll see if i can dig up an ETM for you.

[Bimmerfanatik]

The wiring for the OBC is tied directly into the wiring for the factory head unit. If you've messed up the wires on the HU, the OBC wont work. Does the radio still work?

I'd suggest checking the fuses in the fuse box that are related to the radio/OBC
then check the wires leading into the OBC to try and match them up for switched and constant power


I'll see if i can dig up an ETM for you.

Oh is it?

There isn't a radio in it, but I can have them throw one in and test it, it might lead us in the right direction.

All fuses are good.

[Bimmerfanatik]

Is there any way to bypass this? It seems silly that something as simple as the OBC is keeping the car from turning over.

[MarkH]

The relay box under the drivers side of the dash, the one you said you fried, is used as part of the code feature in the OBC. IIRC, this box will shut off the power to the fuel pump when the code feature is activated.

[Bimmerfanatik]

The relay box under the drivers side of the dash, the one you said you fried, is used as part of the code feature in the OBC. IIRC, this box will shut off the power to the fuel pump when the code feature is activated.

Ok, we're on the right track here.

I don't believe I fried the box, as the plug I was jumping was not plugged into it when it caught up in smoke. But, I did try another box, with no luck, just to be sure.

My first question is, how did the car function beforehand if the plug was not in the box, and what pins could have been jumped to make this work? How can I bypass or reset this feature in order to get the car running again?

Also, does it matter where the OBC comes from? I thought they all worked in any model - perhaps this isn't true? Does the OBC even have to be plugged in?

[Febi Guibo]

hey, real quick... I had a scare induced a couple of weeks ago (my hamster-sized brain) ...have you checked your battery??

I say this because I was doing some instrument cluster work, but ran the car with the cluster removed... it ran my battery to less than 10 volts... car would have power (eg, lights etc.) but no crank... the alternator won't charge with the cluster removed...

I thought it was the obc because fiddling with the cluster harness I yanked (a little) on the OBC... but twas not the case...

check the battery...